Considering, for example, ski boots, it is desirable that the foot of the skier rest perfectly and form-fittingly on the bottom of the ski boot so that the skier can ski without tiring and can impart to the ski the necessary movements without the development of play between the foot and the boot prejudicial to the practice of skiing, particularly to a good "prise de carre".
To achieve this goal it is thus known to place at the interior of the ski boot insoles accurately reproducing the anatomic shape of the foot; and it is thus also known to form such insoles of foils constituted of thermoplastic material.